Current-dependent extension of the Perdew-Burke-Ernzerhof exchange-correlation functional

Selective Interfacial Excited-State Carrier Dynamics and Efficient Charge Separation in Borophene-Based Heterostructures

Borophene-based van der Waals heterostructures have demonstrated enormous potential in the realm of optoelectronic and photovoltaic devices, which has sparked a wide range of interest. However, a thorough understanding of the microscopic excited-state electronic dynamics at interfaces is lacking, which is essential for determining the macroscopic optoelectronic and photovoltaic performance of borophene-based devices. In this study, photoexcited carrier dynamics of β12 , χ3 , and α΄ borophene/MoS2 heterostructures are systematically studied based on time-domain nonadiabatic molecular dynamics simulations. Different Schottky contacts are found in borophene/semiconductor heterostructures. The interplay between Schottky barriers, electronic coupling, and the involvement of different phonon modes collectively contribute to the unique carrier dynamics in borophene-based heterostructures. The diverse borophene allotropes within the heterostructures exhibit distinct and selective carrier transfer behaviors on an ultrafast timescale: electrons tunnel into α΄ borophene with an ultrafast transfer rate (≈29 fs) in α΄/MoS2 heterostructures, whereas β12 borophene only allows holes to migrate with a lifetime of 176 fs. The feature enables efficient charge separation and offers promising avenues for applications in optoelectronic and photovoltaic devices. This study provides insight into the interfacial carrier dynamics in borophene-based heterostructures, which is helpful in further design of advanced 2D boron-based optoelectronic and photovoltaic devices.

Optical excitations of graphene-like materials: group III-nitrides

By using first-principles calculations, we have studied the electronic and optical characteristics of group III-nitrides, such as BN, AlN, GaN, and InN monolayers. The optimized geometry, quasi-particle energy spectra, charge density distributions, band-decomposed charge densities, and Van Hove singularities in density of states are described in the work using physical and chemical pictures and orbital hybridizations found in B-N, Al-N, Ga-N, and In-N chemical bonds. Moreover, the dielectric functions, energy loss functions, absorption coefficients, and reflectance spectra with electron-hole interactions of optical properties are successfully achieved. More importantly, the close relations between electronic and optical properties are successfully demonstrated. The theoretical framework will be useful to research other graphene-like materials.

Theoretical investigations of the electronic and optical properties of a GaGeTe monolayer

Our study focused on exploring the electronic and optical characteristics of the GaGeTe monolayer using first-principles calculations. Our findings showed that this material has remarkable physical and chemical properties attributed to its unique band structure, van Hove singularities in the density of states (DOS), charge density distributions, and charge density differences. We also observed excitonic effects, multiple optical excitation peaks, and strong plasmon modes in the energy loss functions, absorption coefficients, and reflectance spectra, which contribute to its enriched optical response. Moreover, we were able to establish a close relationship between the orbital hybridizations of the initial and final states with each optical excitation peak. Our results suggest that GaGeTe monolayers hold great potential for various semiconductor applications, especially those involving optics. Furthermore, the theoretical framework we used can be applied to study the electronic and optical properties of other graphene-like semiconductor materials.

Adsorption Properties of NF3 and N2O on Al- and Ga-Doped Graphene Surface: A Density Functional Theory Study

SF6/N2 gas mixture decomposition components can reflect the operation status inside GIS, and be used for fault diagnosis and monitoring inside GIS. NF3 and N2O are the characteristic decomposition components of SF6/N2 mixed gas. In order to find a potential gas sensitivity material for the detection of NF3 and N2O. This paper investigated the adsorption properties of NF3 and N2O on Al- and Ga- doped graphene monolayers based on density functional theory. Through the analysis of adsorption distance, charge transfer, adsorption energy, energy band structure, etc., the results indicated that the adsorption effect of Al- and Ga-doped graphene to NF3 and N2O are probably good, and these nanomaterials are potential to apply for the monitoring of GIS internal faults.

First-principles studies of defect behaviour in bismuth germanate

Intrinsic defects are known to greatly affect the structural and electronic properties of scintillators thereby impacting performance when these materials are in operation. In order to overcome this effect, an understanding of the defect process is required for the design of more stable materials. Here we employed density functional theory calculations and the PBE0 hybrid functional to study the structural, electronic,defect process and optical properties of [Formula: see text] (BGO), a well know material used as scintillator. We examined possible intrinsic defects and calculated their formation energy and their impact on the properties that affect the scintillation process. Furthermore, we investigated the effect and role of rare earth element (REE = Nd, Pr, Ce and Tm) doping on the properties of the BGO system. While the PBE functional underestimated the band gap, the PBE0 was found to adequately describe the electronic properties of the system. Out of all the defects types considered, it was found that [Formula: see text] antisite is the most favourable defect. Analysis of the effect of this defect on the electronic properties of BGO revealed an opening of ingap states within the valence band. This observation suggests that the [Formula: see text] could be a charge trapping defect in BGO. We found that the calculated dopant substitution formation energy increases with increase in the size of the dopant and it turns out that the formation of O vacancy is easier in doped systems irrespective of the size of the dopant. We analyzed the optical spectra and noted variations in different regions of the photon energy spectra.

Computational Development of Inhibitors of Plasmid-Borne Bacterial Dihydrofolate Reductase

Resistance to trimethoprim and other antibiotics targeting dihydrofolate reductase may arise in bacteria harboring an atypical, plasmid-encoded, homotetrameric dihydrofolate reductase, called R67 DHFR. Although developing inhibitors to this enzyme may be expected to be promising drugs to fight trimethoprim-resistant strains, there is a paucity of reports describing the development of such molecules. In this manuscript, we describe the design of promising lead compounds to target R67 DHFR. Density-functional calculations were first used to identify the modifications of the pterin core that yielded derivatives likely to bind the enzyme and not susceptible to being acted upon by it. These unreactive molecules were then docked to the active site, and the stability of the docking poses of the best candidates was analyzed through triplicate molecular dynamics simulations, and compared to the binding stability of the enzyme–substrate complex. Molecule 32 ([6-(methoxymethyl)-4-oxo-3,7-dihydro-4H-pyrano[2,3-d]pyrimidin-2-yl]methyl-guanidinium) was shown by this methodology to afford extremely stable binding towards R67 DHFR and to prevent simultaneous binding to the substrate. Additional docking and molecular dynamics simulations further showed that this candidate also binds strongly to the canonical prokaryotic dihydrofolate reductase and to human DHFR, and is therefore likely to be useful to the development of chemotherapeutic agents and of dual-acting antibiotics that target the two types of bacterial dihydrofolate reductase.

Theoretical exploration of mechanical, electronic structure and optical properties of aluminium based double halide perovskite

The mechanical, electronic structure and optical properties of aluminium based double halide perovskite were calculated by density functional theory. The formation energy and elastic constant confirm the stability of the cubic perovskite materials. The materials are all ductile and suitable for flexible photovoltaic and optoelectronic devices. The band gap values vary from 0.773 eV to 3.430 eV, exactly corresponding to the range of ideal band gap values for good photoresponse. The band structure analysis shows that all the materials possess small effective mass, which indicates a good transport of carriers. And these materials have a broad energy range of optical absorption for utilization and a detector of photons. Moreover, less expensive K₂AgAlBr₆ were investigated for comparison with materials containing a cesium element, and according to the results, is also a candidate for photoelectronic devices due to the similar properties.

M₂AgAlX₆ (M = Cs, Rb and K, X = Cl, Br and I) is a stable vacancy ordered double halide perovskite direct band gap semiconductor material with good absorption of near-ultraviolet and short-wavelength visible light.

Computational data of molybdenum disulfide/graphene bilayer heterojunction under strain

The data presented in this paper refer to the research article "Dry and Hydrated Defective Molybdenum Disulfide/Graphene Bilayer Heterojunction Under Strain for Hydrogen Evolution from Water Splitting: A First-principle Study". Here, we present the Density Functional Theory (DFT) data used to generate optimal geometries and electronic structure for the MoS₂/graphene heterostructure under strain, for dry and hydrated pristine and defect configurations. We also report DFT data used to obtain hydrogen Gibbs free energies for adsorption on the MoS₂ monolayer and on graphene of the heterostructure. The DFT data were calculated using the periodic DFT code CRYSTAL17, which employs Gaussian basis functions, under the hybrid functionals PBE0 and HSE06. Moreover, we also report the data used for Quantum Theory of Atoms in Molecules (QTAIM) and Non-covalent Interaction (NCI) analysis calculations. These data were obtained using the optimized unit cell configurations from the periodic DFT and inputted to Gamess program, thus generating files that could be read by the Multiwfn program used for QTAIM and NCI calculations.

Heteroctanuclear Au4Ag4 Cluster Complexes of 4,5-Diethynylacridin-9-One with Luminescent Mechanochromism

Two heteroctanuclear Au₄Ag₄ cluster complexes of 4,5-diethynylacridin-9-one (H₂L) were prepared through the self-assembly reactions of [Au(tht)₂](CF₃SO₃), Ag(tht)(CF₃SO₃), H₂L and PPh₃ or PPh₂Py (2-(diphenylphosphino)pyridine). The Au₄Ag₄ cluster consists of a [Au₄L₄]^4- and four [Ag(PPh₃)]⁺ or [Ag(PPh₂Py)]⁺ units with Au₄L₄ framework exhibiting a twisted paper clip structure. In CH₂Cl₂ solutions at ambient temperature, both compounds show ligand fluorescence at ca. 463 nm as well as phosphorescence at 650 nm for 1 and 630 nm for 2 resulting from admixture of ³IL (intraligand) of L ligand, ³LMCT (from L ligand to Au₄Ag₄) and ³MC (metal-cluster) triplet states. Crystals or crystalline powders manifest bright yellow-green phosphorescence with vibronic-structured emission bands at 530 (568sh) nm for complex 1 and 536 (576sh) nm for complex 2. Upon mechanical grinding, yellow-green emission in the crystalline state is dramatically converted to red luminescence centered at ca. 610 nm with a drastic redshift of the emission after crystal packing is destroyed.

Corrosion Protection Oxide Scale Formed on Surface of Fe-Ni-M (M = Al, Cr, Cu) Inert Anode for Molten Salt Electrolysis

An oxide scale formed on the surface of metal anodes is crucial for determining the overall quality of molten salt electrolysis (MSE), particularly for the durability of the anode materials. However, the material properties of oxide scales are yet to be revealed, particularly in ternary spinel oxide phases. Therefore, we investigate the mechanical and thermal properties of spinel oxides via first-principles calculations. The oxides are calculated using the models of normal (cubic) and inverse (orthorhombic) spinel compounds. The d-orbital exchange correlation potential of transition metal oxides is addressed using the generalized gradient approximation plus Hubbard U. The lattice constant, formation energy, cohesive energy, elastic modulus, Poisson's ratio, universal anisotropy index, hardness, minimal thermal conductivity, and thermal expansion coefficient are calculated. Based on the calculated mechanical and thermal properties of the spinel compound, the Fe-Ni-Al inert anode is expected to be the most suitable oxide scale for MSE applications among the materials investigated in our study.

First-Principle Study of Rh-Doped Nitrogen Vacancy Boron Nitride Monolayer for Scavenging and Detecting SF6 Decomposition Products

The scavenging and detection of sulfur hexafluoride (SF6) decomposition products (SO2, H2S, SO2F2, SOF2) critically matters to the stable and safe operation of gas-insulated switchgear (GIS) equipment. In this paper, the Rh-doped nitrogen vacancy boron nitride monolayer (Rh-VNBN) is proposed as a gas scavenger and sensor for the above products. The computational processes are applied to investigate the configurations, adsorption and sensing processes, and electronic properties in the gas/Rh-VNBN systems based on the first-principle calculations. The binding energy (Eb) of the Rh-VNBN reaches -8.437 eV, while the adsorption energy (Ead) and band gap (BG) indicate that Rh-VNBN exhibits outstanding adsorption and sensing capabilities. The density of state (DOS) analysis further explains the mechanisms of adsorption and sensing, demonstrating the potential use of Rh-VNBN in sensors and scavengers of SF6 decomposition products. This study is meaningful as it explores new gas scavengers and sensors of SF6 decomposition products to allow the operational status assessment of GIS equipment.

Enhanced photocatalytic activity of phosphorene under different pH values using density functional theory (DFT)

Phosphorene, a new two-dimensional material, was investigated theoretically as a promising photocatalyst material. The structural and electronic properties of phosphorene were studied using hybrid functional based HSE approximation. The effect of the adsorbed molecules on the phosphorene surface was studied for various chemical elements, such as water molecule (H₂O), hydronium ion (H₃O⁺), hydrogen atom and ion (H/H⁺), hydroxide molecule (OH), and hydroxide ion (OH⁻). The potential application of phosphorene as a photocatalyst in vacuum was proved under different pH values. A pH of 8 was found to be the suitable value for clean phosphorene in which the flat band position was corrected for the oxidizing and reducing potentials of phosphorene, but the presence of OH⁻ ions in a basic solution damaged the surface structure and limited the use of phosphorene in photocatalysis caused by the high content (0.25 ML and 0.5 ML) of the adsorbed OH⁻ on the phosphorene surface. The obtained results matched the required parameters of a photocatalyst for water splitting using clean phosphorene surface in neutral solution (pH = 7).

Phosphorene, a new two-dimensional material, was investigated theoretically as a promising photocatalyst material.

Enabling Enhanced Lithium Ion Storage Performance of Graphdiyne by Doping with Group-15 Elements: A First-Principles Study

As a typical two-dimensional material possessing sp and sp² hybrid orbitals, graphdiyne (GDY) and its derivatives have been proposed as an attractive candidate for high-performance lithium ion batteries (LIBs). In this work, an advanced GDY LIB electrode is designed by doping with group-15 elements. With the aid of first-principles simulations, the geometric properties, electronic structures, theoretical storage capacities, open-circuit voltages, and diffusion path of Li atoms on doped GDY are comprehensively investigated. Specifically, 14 different adsorption sites are proposed, most of which are situated out of plane of the carbon network, resulting from the out of plane Pz orbitals of conduction band minimum and valence band maximum. Among the five doped GDY, phosphorus-doped graphdiyne (P-GDY) exhibits prominent lithium ion storage behavior, i.e., the maximum theoretical capacity is 1949 mA·h·g^-1, which is ∼2.6 times higher than that of GDY. Moreover, calculation results in terms of the in-plane migration of lithium ion on P-GDY indicate that Li atoms prefer to diffuse across the carbon network (with a moderate barrier of 0.46 eV) rather than directly through the middle of the hexagonal aperture (with a higher barrier of 1.78 eV). Thus, this approach provides novel insights into the Li ion storage properties of group-15 element-doped GDY from the prospect of theoretical calculations, which would be useful to guide the future design of high-capacity GDY anodes for LIBs.

Tellurium-oxygen group enhanced birefringence in tellurium phosphates: a first-principles investigation

Phosphates possess a relatively large UV/DUV cutoff edge, but these compounds usually have very small birefringence. Recently the Te₂P₂O₉ crystal was synthesized and its birefringence was reported to be as large as 0.106 at 1013.98 nm. Herein, we investigated the electronic structure and optical properties of Te₂P₂O₉ using the first-principles method. The obtained results are in good agreement with the experimental values. The Born effective charges and SHG density of Te₂P₂O₉ show that the contribution to the birefringence and SHG response mainly originates from the TeO₅ group. The electronic structures and optical response of Ba₂TeO(PO₄)₂ and Te₃O₃(PO₄)₂ were also investigated for comparison. The results show that these two tellurium phosphates also possess a large birefringence similar to Te₂P₂O₉. Also, the birefringence originates from the TeO _x polyhedrons, which was confirmed by the real-space atom-cutting results and distortion indices.

Au Catalyst-Modified MoS2 Monolayer as a Highly Effective Adsorbent for SO2F2 Gas: A DFT Study

To ensure the stable operation of gas-insulated equipment, removal of SF₆ decomposition products of sulfur hexafluoride (SF₆) is one of the best methods. SO₂F₂ is one of the typical decomposition products of SF₆, while the Au-modified MoS₂ (Au-MoS₂) monolayer is a novel gas adsorbent. Therefore, based on the first-principles calculation, the adsorption properties of the SO₂F₂ molecule on the Au-MoS₂ monolayer are calculated. Furthermore, the adsorption energy, charge transfer, and structure parameters were analyzed to obtain the most stable adsorption structure. These results indicate that all of the adsorption processes are exothermic. To better study the adsorption mechanism between the SO₂F₂ molecule and the Au-MoS₂ monolayer, the density of states, the highest occupied molecular orbital, the lowest unoccupied molecular orbital, and electron density difference were obtained. At last, we conclude that the interaction between the SO₂F₂ molecule and the Au-MoS₂ monolayer was chemisorption. This study provides a theoretical basis to prepare the Au-MoS₂ monolayer for the removal of SF₆ decomposition products.

Strain Control of the Tunable Physical Nature of a Newly Designed Quaternary Spintronic Heusler Compound ScFeRhP

Recently, an increasing number of rare-earth-based equiatomic quaternary compounds have been reported as promising novel spintronic materials. The rare-earth-based equiatomic quaternary compounds can be magnetic semiconductors (MSs), spin-gapless semiconductors (SGSs), and half-metals (HMs). Using first-principle calculations, we investigated the crystal structure, density of states, band structure, and magnetic properties of a new rare-earth-based equiatomic quaternary Heusler (EQH) compound, ScFeRhP. The results demonstrated that ScFeRhP is a HM at its equilibrium lattice constant, with a total magnetic moment per unit cell of 1 μB. Furthermore, upon introduction of a uniform strain, the physical state of this compound changes with the following transitions: non-magnetic-semiconductor-(NMS) → MS → SGS → HM → metal. We believe that these results will inspire further studies on other rare-earth-based EQH compounds for spintronic applications.

A DFT Study on the Adsorption of H₂S and SO₂ on Ni Doped MoS₂ Monolayer

In this paper, a Ni-doped MoS₂ monolayer (Ni-MoS₂) has been proposed as a novel gas adsorbent to be used in SF₆-insulated equipment. Based on the first-principles calculation, the adsorption properties of Ni-MoS₂ to SO₂ and H₂S molecules, the main decomposition components of SF₆ under a partial discharge (PD) condition have been studied. The adsorption energy, charge transfer, and structural parameters have been analyzed to find the most stable gas-adsorbed Ni-MoS₂. Furthermore, the density of states (DOS), projected density of states (PDOS), and electron density difference were employed to explore the interaction mechanism between SO₂, H₂S, and the Ni-MoS₂ surface. It is found that the H₂S molecule and SO₂ molecule interact with the Ni-MoS₂ surface by strong adsorption energy. Therefore, we conclude that the interaction between these two kinds of gases and the Ni-MoS₂ monolayer belongs to chemisorption, and the Ni-MoS₂ monolayer might be a promising gas adsorbent for the fault recovery of SF₆-insulated equipment. Additionally, we have to point out that all of the conclusions only considered the final adsorption energy, the barrier in the transition state has not been analyzed in this paper.

New Half-Metallic Materials: FeRuCrP and FeRhCrP Quaternary Heusler Compounds

The electronic structures and magnetic properties of FeRuCrP and FeRhCrP quaternary Heusler compounds with LiMgPbSb-type structures have been investigated via first-principles calculations. The calculational results show that both FeRuCrP and FeRhCrP compounds present perfect half-metallic properties: Showing large half-metallic band gaps of 0.39 eV and 0.38 eV, respectively. The total magnetic moments of FeRuCrP and FeRhCrP are 3 μB and 4 μB per formula unit, respectively. The magnetism of them mainly comes from the 3d electrons of Cr atoms and follows the Slater-Paulig behavior of Heusler compounds: Mt = Zt - 24. Furthermore, the half-metallic properties of FeRuCrP and FeRhCrP compounds can be kept in a quite large range of lattice constants (about 5.44-5.82 Å and 5.26-5.86 Å, respectively) and are quite robust against tetragonal deformation (c/a ratio in the range of 0.94-1.1 and 0.97-1.1, respectively). Moreover, the large negative cohesion energy and formation energy of FeRuCrP and FeRhCrP compounds indicate that they can be synthesized experimentally.

Gauging the flexibility of the active site in soybean lipoxygenase-1 (SLO-1) through an atom-centered density matrix propagation (ADMP) treatment that facilitates the sampling of rare events

We present a computational methodology to sample rare events in large biological enzymes that may involve electronically polarizing, reactive processes. The approach includes simultaneous dynamical treatment of electronic and nuclear degrees of freedom, where contributions from the electronic portion are computed using hybrid density functional theory and the computational costs are reduced through a hybrid quantum mechanics/molecular mechanics (QM/MM) treatment. Thus, the paper involves a QM/MM dynamical treatment of rare events. The method is applied to probe the effect of the active site elements on the critical hydrogen transfer step in the soybean lipoxygenase-1 (SLO-1) catalyzed oxidation of linoleic acid. It is found that the dynamical fluctuations and associated flexibility of the active site are critical toward maintaining the electrostatics in the regime where the reactive process can occur smoothly. Physical constraints enforced to limit the active site flexibility are akin to mutations and, in the cases studied, have a detrimental effect on the electrostatic fluctuations, thus adversely affecting the hydrogen transfer process.

Orbital currents in the Colle-Salvetti correlation energy functional and the degeneracy problem

Popular density functionals for the exchange-correlation energy typically fail to reproduce the degeneracy of different ground states of open-shell atoms. As a remedy, functionals which explicitly depend on the current density have been suggested. We present an analysis of this problem by investigating functionals that explicitly depend on the Kohn-Sham orbitals. Going beyond the exact-exchange approximation by adding correlation in the form of the Colle-Salvetti functional, we show how current-dependent terms enter the Colle-Salvetti expression and their relevance is evaluated. A very good description of the degeneracy of ground states for atoms of the first and second rows of the Periodic Table is obtained.

On the degeneracy of atomic states within exact-exchange (spin-) density functional theory

The problem of degenerate ground states of open-shell atoms is investigated in spin-restricted and spin-unrestricted density functional theories using the exact-exchange energy functional. For the spin-unrestricted case, spurious energy splittings of the order of 2-3 kcal/mol are found for atoms of the second and third periods which are larger than the splittings obtained from recently proposed approximate exchange functionals depending explicitly on the current density. In remarkable contrast, for spin-restricted calculations the degeneracy of different atomic ground states is recovered to within less than 0.6 kcal/mol.

Nonempirical construction of current-density functionals from conventional density-functional approximations

Density-functional approximations for the exchange-correlation energy Exc[n] of a many-electron ground state are highly developed and widely useful. When a paramagnetic current jp(r) is present, Vignale and Rasolt have extended the Kohn-Sham theorems and presented an additive correction valid to second order in the gauge-invariant vorticity nu=Delta x (jp/n):Exc[n, jp]=Exc[n, jp=0] + DeltaE(VR)(xc)[n, nu]. Apart from spin-polarization effects, their correction is unambiguous for a generalized gradient approximation (GGA). But for a meta-GGA (MGGA), one needs to know how to go back from the orbital kinetic energy density tau([n, jp];r) to tau([n,0];r); we show how to do this here. Numerical tests on the degeneracies for open-shell atoms show that current-density corrections reduce the error of GGA from 2 to 1 kcal/mol, and of MGGA from 5 to 2 kcal/mol.

Generalized density functional theory for degenerate states

An extension of density functional theory is proposed for degenerate states. There are suitably selected basic variables beyond the subspace density. Generalized Kohn-Sham equations are derived. A direct method is proposed to ensure the fixed value of ensemble quantities. Then the Kohn-Sham equations are similar to the conventional Kohn-Sham equations. But the Kohn-Sham potential is different for different ensembles. A simple local expression is proposed for the correlation energy.

Relativistic all-electron two-component self-consistent density functional calculations including one-electron scalar and spin–orbit effects

We have implemented a Gaussian basis-set two-component self-consistent field method based on the fourth-order nuclear-only Douglas-Kroll-Hess approximation. Two-electron spin-orbit effects are included using Boettger's screened-nuclear spin-orbit approximation. In our two-component approach, the spin-orbit interaction is taken into account in a variational fashion employing a generalized Kohm-Sham scheme which allows one to work with hybrid density functionals. For open-shell systems we adopt the noncollinear spin-density approximation. Results are presented for equilibrium bond lengths, harmonic vibrational frequencies, and bond dissociation energies with local spin-density, generalized gradient approximation, and hybrid functionals in a set of benchmark molecules.